fixed model gen for multiple implemented type

plugin/modelgen/models.go

@@ -110,8 +110,23 @@ func (m *Plugin) MutateConfig(cfg *config.Config) error {
 				Description: schemaType.Description,
 				Name:        schemaType.Name,
 			}
+
+			// If Interface A implements interface B, and Interface C also implements interface B
+			// then both A and C have methods of B.
+			// The reason for checking unique is to prevent the same method B from being generated twice.
+			uniqueMap := map[string]bool{}
 			for _, implementor := range cfg.Schema.GetImplements(schemaType) {
-				it.Implements = append(it.Implements, implementor.Name)
+				if !uniqueMap[implementor.Name] {
+					it.Implements = append(it.Implements, implementor.Name)
+					uniqueMap[implementor.Name] = true
+				}
+				// for interface implements
+				for _, iface := range implementor.Interfaces {
+					if !uniqueMap[iface] {
+						it.Implements = append(it.Implements, iface)
+						uniqueMap[iface] = true
+					}
+				}
 			}
 
 			for _, field := range schemaType.Fields {

plugin/modelgen/models_test.go

@@ -6,6 +6,7 @@ import (
 	"go/token"
 	"io/ioutil"
 	"path/filepath"
+	"sort"
 	"strings"
 	"testing"
 
@@ -177,6 +178,38 @@ func TestModelGeneration(t *testing.T) {
 			})
 		}
 	})
+
+	t.Run("implemented interfaces type CDImplemented", func(t *testing.T) {
+		pkg, err := parseAst("out")
+		require.NoError(t, err)
+
+		path := filepath.Join("out", "generated.go")
+		generated := pkg.Files[path]
+
+		wantMethods := []string{
+			"IsA",
+			"IsB",
+			"IsC",
+			"IsD",
+		}
+
+		gots := make([]string, 0, len(wantMethods))
+		for _, decl := range generated.Decls {
+			if funcDecl, ok := decl.(*ast.FuncDecl); ok {
+				switch funcDecl.Name.Name {
+				case "IsA", "IsB", "IsC", "IsD":
+					gots = append(gots, funcDecl.Name.Name)
+					require.Len(t, funcDecl.Recv.List, 1)
+					recvIdent, ok := funcDecl.Recv.List[0].Type.(*ast.Ident)
+					require.True(t, ok)
+					require.Equal(t, "CDImplemented", recvIdent.Name)
+				}
+			}
+		}
+
+		sort.Strings(gots)
+		require.Equal(t, wantMethods, gots)
+	})
 }
 
 func mutateHook(b *ModelBuild) *ModelBuild {

plugin/modelgen/testdata/schema.graphql

@@ -124,4 +124,11 @@ interface D implements A & B {
     a: String!
     b: Int!
     d: String
+}
+
+type CDImplemented implements C & D {
+    a: String!
+    b: Int!
+    c: Boolean!
+    d: String
 }